1. Field of the Invention
The present invention relates to an apparatus for etching or stripping a substrate of a liquid crystal display device and method thereof.
2. Discussion of the Related Art
Generally, a liquid crystal display device has characteristics of low-voltage driving, full-color realization, light weight, compact size, and the like. Applicable fields of the liquid crystal display device extend to PDA, wide-screen TV, airplane monitors, calculators, watches, notebook computers, and the like. Such characteristics of the liquid crystal display device are fundamentally attributable to the use of thin film transistors.
A process of fabricating a thin film transistor in a liquid crystal display device includes the repeated steps of deposition, photoresist coating, mask installment, exposure, etching, stripping, and the like for forming a predetermined pattern.
The etching and stripping processes can be performed by dry or wet methods. Yet, in order to increase yield, shorten process time, save costs, and attain a well-patterned thin film transistor, the wet method is widely used. In this case, the wet method for the etching or stripping process is carried out in a manner wherein a substrate is placed into a reaction vessel filled with a liquid compound (etchant or stripper).
Hence, exchange of the compound solution (etchant or stripper) is required for the wet method.
A process of etching or stripping a substrate for a liquid crystal display device according to a related art process is explained by referring to the attached drawings as follows.
FIG. 1 illustrates a diagram of a related art apparatus for etching or stripping a substrate of a liquid crystal display device.
Referring to FIG. 1, substrates are loaded on a loader 100. In this case, it is assumed that deposition of required materials, photoresist coating, mask installment, and exposure of the photoresist have been carried out on the substrates. Meanwhile, the substrates are stacked separately in the loader 100. Then the substrates are conveyed through rollers.
In the substrate-proceeding direction shown in FIG. 1, the substrates are conveyed to a first neutral part 101a from the loader 100. The first neutral part 101a is a unit for progressing the substrates forward, and no processing is carried out in the first neutral part 101a. The first neutral part 101a includes an upper unit, a lower unit, and a convey roller (not shown).
The substrates having passed the first neutral part 101a are transferred to an etching reaction vessel 102 filled with an etchant for an etching process. In this case, a strong acidic solution is used as the etchant. The etching reaction vessel 102 includes at least three equivalent etching zones (not shown). The substrates pass the three etching zones for about 100 seconds so as to be etched. And, the three etching zones are connected to a single etchant tank, and a plurality of sprays (not shown) are installed at each of the etching zones. The sprays spray the etchant on the substrates simultaneously. Material on the substrate is removed in accordance with a desired pattern and the used etchant is returned to the etchant tank through a roller bath.
After completion of the etching process, the substrates enter a first cleaning unit 103 from the etching reaction vessel 102.
The substrates having passed the first cleaning unit 103 are transferred to the stripping apparatus in FIG. 1 for stripping processes that will be carried out successively. First of all, the substrates pass a second neutral part 101b. The second neutral part 101b is a unit for progressing the substrates forward, and no processing is performed in the second neutral unit 101b. The second neutral unit 101b includes an upper unit, a lower unit, and a convey roller (not shown).
The substrates having passed the second neutral part 101b enter a stripping reaction vessel 105 filled with a stripping solution. In this case, a strong alkaline solution is used as the stripping solution. The substrates are stripped in the stripping reaction vessel 105 for a predetermined time, and then discharged from the stripping reaction vessel 105.
After completion of the stripping process, the substrates are transferred to a second cleaning unit 106. A second cleaning process is carried out on the substrates in the second cleaning unit 106. After completion of the second cleaning process, the substrates are dried in a dry unit 107, and then transferred to an unloader 109.
In this case, the etchant tank of the etching reaction vessel 102 and the stripping tank of the stripping reaction vessel 105 are used for etching a number of the substrates, and then should be replaced by new etchant tanks. Hence, spare etchant tanks are required.
A method of replacing the tank in the apparatus according to the related art is explained by referring to FIG. 2 as follows.
FIG. 2 illustrates a flowchart of a process of exchanging an etchant tank of the apparatus in FIG. 1.
Referring to FIG. 2, it is assumed that the etching process is being carried out in the etching reaction vessel 102. In this case, it is also assumed that a first etchant tank 102a is used as the first etchant tank. Subsequently, it is checked whether the substrates etched by the etchant of the first etchant tank 102a attain a maximum substrate number available for the first etchant tank (S2). In this case, the previously set maximum substrate number is nine hundred.
If the number of the substrates etched by the etchant of the first etchant tank 102a is lower than nine hundred as the maximum substrate number, the substrates are continuously produced using the etchant of the first etchant tank 102a (S1). If the number is greater than or equal to nine hundred, a readiness state of a second etchant tank 102 is checked (S3).
If the second etchant tank 102a is not in a state of readiness, an alarm informing of a condition of abnormality of the apparatus is generated and the loader stops loading the substrates. Moreover, the substrate conveying unit and a substrate circulating unit in the apparatus are stopped. Meanwhile, if the second etchant tank 102b is in readiness, the first etchant tank 102a is replaced by the second etchant tank 102b. Hence, the etchant in the second etchant tank is supplied to the etching reaction vessel 102 and the contents of the first etchant tank 102a is entirely discharged outside (S4).
Subsequently, it is sensed whether the etchant in the first etchant tank 102a is discharged completely by a position sensor (S5). After a predetermined delay time goes by, the first etchant tank 102a is supplied with a new etchant (S6) and the first etchant tank 102a is heated (S8).
It is then checked by the position sensor whether the first etchant tank 102a is supplied with a required amount of the etchant (S9). Then it is checked by a temperature sensor whether the etchant in the first etchant tank 102a is in the required temperature range (S10).
Thereafter, it is checked whether the first etchant tank 102a is in readiness or not (S11, S12).
Unfortunately, the apparatus and method according to the related art have the following problems or disadvantages.
First of all, the apparatus is constituted in a manner such that the tanks are exchanged with each other by every setup value. Yet, there is no function of checking previously whether the tanks for the exchange are in readiness or not. If the tanks failing to be in readiness are exchanged, the substrates in progress in the apparatus are stuck in the apparatus so as to generate problems such as over-etching. Hence, failures of the liquid crystal display device occur.
Secondly, when failures occur, increased handling costs associated with the failed substrates cause unnecessary waste.
Thirdly, the etchant tanks are exchanged after removal of the failed substrates, thereby prolonging downtime of the apparatus.